Hard disk drives include one or more rigid disks, which are coated with a magnetic recording medium in which data can be stored. Hard disk drives further include read and write heads for interacting with the data in the magnetic recording medium. The write head includes an inductive element for generating a magnetic field that aligns the magnetic moments of domains in the magnetic recording medium to represent bits of data.
Magnetic recording techniques include both longitudinal and perpendicular recording. Perpendicular magnetic recording (“PMR”) is a form of magnetic recording in which the magnetic moments representing bits of data are oriented perpendicularly to the surface of the magnetic recording medium, as opposed to longitudinally along a track thereof. PMR enjoys a number of advantages over longitudinal recording, such as significantly higher areal density recording capability.
Some PMR write poles are provided with a bevel near the air bearing surface, which allows the majority of the write pole to have a large thickness while providing a desirable thin pole tip. Forming such a bevel in a PMR write pole presents numerous manufacturing challenges, as does the accurate determination of the bevel angle produced by various fabrication processes. Because a PMR write pole is very small (e.g., frequently having a track width of less than 100 nm), the direct measurement of the angle thereof is painstakingly difficult and frequently unreliable.